But K Street had held out hope that somehow, someway, Baucus and Camp would make the seemingly impossible happen.

Now, with Baucus likely moving out of the picture to become the U.S. ambassador to China, the divide between the parties on the revenue question appears more daunting than ever.

“A driving force for this effort has been Sen. Baucus,” said Micah Green, co-chairman of Patton Boggs’s financial services and tax practice. “Him stepping out of that role raises natural questions about the timing of this effort.”

“For those who want to see tax reform done, if it doesn't get done before Sen. Baucus leaves, Wyden is a good choice,” said Jade West, senior vice president of government relations of the National Association of Wholesaler-Distributors.

Ryan made clear this week what many had long expected — that he wants to take over the Ways and Means Committee gavel in 2015, since Camp is term limited.

With few expecting tax reform to get done next year, that would mean that the tax chairmen in the next Congress would already start with a solid working relationship.

Still, Republicans seeking tax reform sooner rather than later caution not to give up on Camp. The Michigan Republican’s principles for tax reform do overlap with Wyden’s, as one House GOP aide pointed out.

Camp and House Republicans, for instance, want to get the top corporate rate down to 25 percent, very close to the 24 percent laid out by Wyden and Coats.

The Wyden-Coats plan also would collapse the current seven individual tax brackets into three — 15 percent, 25 percent and 35 percent. That top rate is 10 percentage points higher than House Republicans are shooting for.

“This thing has been vetted,” Coats said about his tax reform bill with Wyden. “It has been worked on a bipartisan basis. There are pieces of this that could be the foundation and building blocks for a truly comprehensive product.”

Wyden, currently the chairman of the Energy and Natural Resources Committee, has also been complimentary of some of the building blocks that Baucus has put into place on tax reform.

He has also pushed to extend expiring tax provisions, especially those for renewable energy, that have been held up so far this year, which could give efforts to retroactively extend those provisions next year a shot in the arm.

Baucus has released four discussion drafts in recent weeks on tax reform, including a draft this week on clean energy incentives that drew quick praise from Wyden.

Still, given that Baucus and Camp have worked nonstop on tax reform for three years now, lobbyists and lawmakers also wonder if any tax panel chairman could successfully get tax reform off the ground in the next several years, even someone like Ryan, who has deep respect among Republicans on fiscal issues.

Wyden, for instance, said Thursday that it looked like House momentum on tax reform had stalled. And Republicans like Thune see little chance that tax reform will rev up in the coming months unless President Obama makes a rewrite of the tax code more of a priority.

“I think the philosophical differences — I don’t expect that changes from Baucus to Wyden or whomever,” the South Dakota Republican said. “I still think their deal is going to be, we need taxes out of this.”

The Democratic leadership in the Senate, and GOP leaders in the House have both seemed lukewarm at best to tax reform in recent months, if for very different reasons.